linux-kernel - Re: [PATCH ipsec-next] xfrm: use complete IPv6 addresses for hash

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Date:   Tue, 16 Oct 2018 10:26:36 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Michal Kubecek <mkubecek@...e.cz>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH ipsec-next] xfrm: use complete IPv6 addresses for hash

On Fri, Oct 12, 2018 at 02:24:44PM +0200, Michal Kubecek wrote:
> In some environments it is common that many hosts share the same lower half
> of their IPv6 addresses (in particular ::1). As __xfrm6_addr_hash() and
> __xfrm6_daddr_saddr_hash() calculate the hash only from the lower halves,
> as much as 1/3 of the hosts ends up in one hashtable chain which harms the
> performance.
> 
> Use complete IPv6 addresses when calculating the hashes. Rather than just
> adding two more words to the xor, use jhash2() for consistency with
> __xfrm6_pref_hash() and __xfrm6_dpref_spref_hash().
> 
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>

Applied to ipsec-next, thanks a lot!